Fitness is a condition of overall health and well being and, more importantly, the capacity to do regular parts of daily activities, jobs and sports. Fitness is normally achieved through physical activity, proper nutrition and enough rest. It is a necessary part of our life that we cannot do without. If we don’t take care of our health, we can suffer from different diseases and even die. Hence, fitness becomes a necessity.
The first and most important aspect of fitness is defined as an organism’s ability to function in the environment. Fitness of an organism refers to the ability of an organism to adapt to its environment. Fitness is defined as the capacity to survive and do well under the given circumstances. Fitness of an organism could be measured directly or indirectly. Fitness could be influenced by genetics, environment, diet, exercise and the body size or shape or some combination of these factors. Therefore, an organism could be considered fit if it survives and does well under the given environmental conditions and it could also be fit if it can perform activities well under the given conditions.
Fitness is directly influenced by the individual’s ability and inclination to use effort and the environment to achieve a goal. Individual differences in aptitude and motivation determine individual fitness. The concept of fitness has been a long standing feature of philosophical discussions. Descartes, Leibniz, Locke, and Aristotle all provided theories of what an organism should be able to do under given circumstances.
Theories of fitness, like all theories in science, are empirical; meaning that they are based on observations. Fitness theories are frequently empirical in nature, because the behavior of the individuals who have established the theoretical framework is often very similar to their behavior in real life. Thus, it is possible to find a range of fitness differences, even between very different organisms. The underlying idea of the different species of organisms having different innate characteristics and aptitudes for living and reproducing has also led to theories of universal fitness. Universal fitness is the tendency of every organism to survive and reproduce within a population unless it is hindered by other factors such as natural barriers or genetic drift.
Fitness theories also include two broad categories of potential fitness: trait fitness and situational fitness. Trait fitness is a general measure of an organism’s quantitative traits, such as intelligence, strength, speed, reproductive success, and reproductive capacity. A trait fitness definition may be quantitative or non Quantitative. Non-Quantitative trait fitnesses are important in defining fitness in relation to the environment and external forces such as gravity, weather conditions, or pollutants. However, trait fitnesses are not the only criteria for defining fitness.
Within a broad spectrum of fitness theories, two competing but closely related ideas remain the subject of debate. According to the competing theory of natural selection, or the theory of evolution, all organisms have been shaped through time by the selective pressures of their environment. Selection can occur on the size of the body (e.g., the size of a tick), the shape of the body (e.g., the flight pattern of a flying insect), the function of the body (e.g., the function of an insect’s eye), or any number of other traits that would affect an organism’s survival and reproduction. The competing theory called the trait fitness view maintains that each individual organism has its own distinct and separate fitness patterns that are based on the prior selection among differing environments.
In order to demonstrate the strength of trait fitness, one must first show that individuals differ in regards to their individual fitness. Fitness is quantified using the sum of all fitness traits of an individual. This is most commonly done through the use of the metrics like Fitness Thresholds, GRE Evolutionary Fitness, or percentile Fitness Thresholds. GRE Fitness is a popular metric used to determine the individual fitness of individuals based on a number of different factors including age, height, weight, and body composition. It was developed by Richard Lazarus and Lawrence Coleman, who showed that fitness for humans evolves very linearly as a function of age.
The other theory of natural selection has to do with ecological fitness. Here, fitness for an organism is described as a combination of various survival and reproductive costs that are necessary for the organism to flourish in its environment. Under this theory, there are different costs that go into optimizing fitness for an organism. These include genetic resources, local adaptation costs, physiological resources, and ecological costs.